The diagram shows a transistor
which explains whether boron or arsenic is the dopant most
likely used in the semiconductor layer marked with +?
this layer is the controller of an npn transistor, so it
could include boron.
this layer is the emitter of an npn transistor, so it could
include arsenic.
this layer is the controller of a pnp transistor, so it could
include arsenic.
this layer is the emitter of a pnp transistor, so it could
include boron.